SharePoint 2013 vs SharePoint ONline

Hello,

I'm trying to understand the key differences between SharePoint 2013 and SharePoint Online from a end-user point of view. In essence I want to help a customer understand 2 things:

1) What changes should users expect with SPO in terms of functionnalities and look&feel?

2) Is there some documentation to guide users accustomed to SP 2013 functionalities to other more useful M365 apps ? For example workflows to Power Automate; or lists to Microsoft List.

Many thanks!